Idiopathic scoliosis (IS) is a structural lateral curvature of the spine present in the late juvenile or adolescent period in otherwise normal individuals. Previous studies from a number of populations have suggested autosomal dominant, X-linked and/or multifactorial modes of inheritance. As part of a large collaborative study of familial idiopathic scoliosis, 200 families (1200 individuals) with at least two individuals with scoliosis have been ascertained and clinically characterized. Phenotypes include degree of lateral curvature, curve type, age of onset and sex. A genome-wide screen for 1200 individuals was performed at the Center for Inherited Disease Research. The families were ranked based on the ratio of the likelihood of each family given an X-linked model relative to that of an autosomal model. The mode of inheritance for families in the upper tail of the distribution was assumed to be X-linked, while that of the families in the lower tail was assumed to be autosomal dominant. Model-dependent and model independent linkage analysis have been completed on subsets of these families based on the ranked distribution from both tails of the distribution. Several candidate regions have been identified, and flanking markers have been typed to corroborate the findings from the genomic screen. At least a portion of the families studied appear to be X-linked, while four autosomal candidate regions are being investigated in the rest of the families.